1. Field of the Invention
The present invention relates to a head suspension assembly of a disk drive having a floating head, such as a magnetic disk drive, optical disk drive, and magneto-optical disk drive, which is used as a recoding and reproducing device for a computer or the like. The head suspension assembly supports the head to move and place the head to a target position above the data-recording surface of a record medium (simply referred to as a “disk”).
2. Background Art
In a disk recording and reproducing device (hereinafter referred to as a “disk drive”), such as a hard disk drive (HDD), a head allows data to be recorded into and reproduced from the recording surface of a disk, i.e. a record medium. A HDD has a head suspension assembly. The head suspension assembly is structured to support the head so that the head floats with a predetermined clearance provided relative to the data recording surface of a record medium and (pivotally) moves radially above the record medium. A large number of proposals including these structures have been made (see the Japanese Patent Unexamined Publication No. H09-82052, for example).
Hereinafter, a description is provided of a head suspension assembly of a magnetic recoding and reproducing device, e.g. a hard disk drive (HDD), as an example of a head suspension assembly of a conventional disk drive having a floating head. The description is provided using FIG. 9, a plan view showing the structure of an essential part of the magnetic recording and reproducing device, and FIG. 10, a perspective view showing a major portion of the head suspension assembly for explanation thereof.
With reference to FIG. 9, head suspension assembly 71 is made up of load beam 72 having relatively low rigidity, leaf spring 73, carriage 74 having relatively high rigidity, slider 75 provided at one end of load beam 72 on a surface opposed to a record medium (disk), and a head (not shown) mounted on this slider 75. Load beam 72 is designed to have relatively low rigidity. The other end of load beam 72 is bent to form resilient member 73 made of a leaf spring or the like. This resilient member 73 is coupled to carriage 74. Further, carriage 74 is pivotally supported by pivotal bearing 76. Driving means 77 attached to carriage 74 allows head suspension assembly 71 to pivotally move in a direction parallel to the surface of record medium 78 in a predetermined range of angles. Head suspension assembly 71, pivotal bearing 76, and driving means 77 constitute head driving mechanism 70.
Record medium 78 is rotated by rotating means 79 at a predetermined speed. When a magnetic recoding and reproducing device records or reproduces data, the balance of floating force caused by airflow resulting from rotation of record medium 78 and force of urging slider 75 toward the surface of record medium 78 causes slider 75 to float with a certain floating amount. The head records and reproduces data while it floats with the certain floating amount. The force of urging slider 75 toward the surface of record medium 78 is exerted mainly by leaf spring 73 of head suspension assembly 71.
In other words, in recording and reproduction of data, driving means 77 provided in carriage 74 moves head suspension assembly 71 pivotally around pivotal bearing 76. Thus, the head mounted on slider 75 is positioned above a specific track while floating above the surface of record medium 78 with a certain floating amount for recording and reproduction of data.
A further description is provided of the structure and operation of head suspension assembly 71, with reference to FIG. 10. FIG. 10 is a perspective view of a major portion of head suspension assembly 71 of FIG. 9 having a magnetic head.
With reference to FIG. 10, a magnetic head (not shown) is provided on slider 75 opposed to a magnetic record medium (not shown). Slider 75 is provided on the bottom face of one end of load beam 72. On the other hand, the other end of load beam 72 is bent to form leaf spring 73. Leaf spring 73 is engaged with carriage 74. In order to prevent changes in the load of slider 75 imposed on a magnetic record medium that are caused by vertical movements (e.g. side-runout) of the magnetic record medium and variations in the distance between the slider and the magnetic record medium caused by mass production, leaf spring 73 has cut-out opening 80. The cut-out opening reduces the rigidity and spring constant of leaf spring 73 and renders leaf spring 73 flexible.
In such a head suspension assembly, even when vertical movements of a disk, i.e. a record medium, occur in recording into and reproduction from the disk, displacement of a head from a specific track position on the disk, which is called off-track, is prevented by stable floating of the slider. Additionally, the head can sufficiently follow the vertical movements of the disk. For these purposes, the head suspension assembly is structured so that a leaf spring mainly exerts force on a slider to cause the slider to impose a predetermined load toward the disk and a load beam has flexibility. Therefore, it is required that the leaf spring ensures the force necessary to urge the slider toward the surface of a disk. On the other hand, the floating amount of the slider varies with the product. Thus, it is also required to prevent variations in the force of urging the slider toward the surface of a disk. For this purpose, as illustrated in FIG. 9, the load beam has a cut-out opening or a thin-sheet structure, which reduces the rigidity and spring constant of the spring. This structure renders a certain degree of flexibility to the head suspension assembly and accommodates variations in urging force.
However, having a load beam of a thin-sheet structure, the conventional head suspension assembly has a low frequency at the main resonance point, i.e. a low resonant frequency. As a result, an oscillation mode including a twist occurs when the head suspension assembly pivotally moves to be positioned above a specific track. It requires a certain period of time to settle this oscillation mode. As a result, it poses a problem of difficulty in reducing access time.
In the conventional head suspension assembly, the center of gravity lies in a position nearer to a portion on which the head is mounted than to the resilient member made of a leaf spring or the like. For this reason, in the slider, strong external shocks given to the magnetic recording and reproducing device will disturb the balance between the floating force caused by airflow generated by rotation of a disk, i.e. a record medium, and the force of urging the slider toward the disk. This is prone to cause phenomena, such as a jump of the slider out of the surface of the disk. Such a jump causes the slider to collide with the record medium and the record medium may have magnetic or mechanical damages.
Providing a cut-out opening or structuring as a thin sheet can reduce the rigidity and spring constant of a spring of a resilient member to accommodate variations in urging force. However, it is difficult to extend the tolerance of variations in spring constant. Additionally, there is almost no ideal design of a spring of a resilient member in which the stress of the spring occurring when the load of a slider is imposed is reduced but the pressing force of the slider can be increased.
These problems are seen in not only the magnetic recording and reproducing device, but also in another disk drive having a floating head, such as an optical disk drive and magneto-optic disk drive.
Additionally, there is a demand for size reduction, especially reduction in the thickness of a magnetic recording and reproducing device. In order to provide a thinner device, reduction in the thickness of a head suspension assembly is required.